Increasing pressures to 30 mmHg in right (RV) and left (LV) ventricles and surrounding heart (SH) in isolated, arrested, maximally vasodilated, blood-perfused dog hearts shifted pressure-flow (PF) curves rightward and increased zero flow pressure (P(zf)) by an amount equal to the RV applied pressure, SH applied pressure, or two-thirds of the LV applied pressure. There were comparable increases ...

Acute aortic valvular insufficiency was induced in open chest dogs by employing a special intravascular cannula, or by rupturing an aortic valve leaflet. Phasic and mean coronary flow were assessed in some animals, while in others data were obtained on arterial and coronary sinus blood lactate, pyruvate, P(O2), P(CO2), and pH, and on myocardial tissue lactate, pyruvate, and water content in the...

At rest the myocardium extracts approximately 75% of the oxygen delivered by coronary blood flow. Thus there is little extraction reserve when myocardial oxygen consumption is augmented severalfold during exercise. There are local metabolic feedback and sympathetic feedforward control mechanisms that match coronary blood flow to myocardial oxygen consumption. Despite intensive research the loca...

Substantial progress has been made toward understanding the pathophysiological processes that lead to acute myocardial infarction. Research has shown that the mechanism of infarction is the rupture of an atherosclerotic plaque with a subsequent thrombogenic response from exposed subendothelial tissue, leading to additional or complete obstruction of the vessel. Myocardial cell death then procee...

To determine the effects of age on the myocardium, the functional and structural characteristics of the heart were studied in rats at 3, 10 to 12 and 19 to 21 months of age. Systemic arterial pressure, left ventricular pressure and its first derivative (dP/dt) and heart rate were comparable in the three animal groups. In the interval between 3 and 10 to 12 months, mean myocyte cell volume per n...

Effects of ectopic pacing on left ventricular repolarization were studied in six anesthetized open-chest chickens. In each animal, unipolar electrograms were acquired from as many as 98 sites with 14 plunge needles (seven transmural locations between epicardium and endocardium in each needle). Activation-recovery intervals (ARIs), corrected to the cycle length, were used for estimating repolari...

During global ischemia in isolated rat hearts, the development of contracture, due to irreversible myofilament sliding, causes reduction of left ventricle luminal volume. Also, a considerable area of the myocardium cannot be reperfused after 1 hour's global ischemia. The purpose of this study was to reduce myofilament sliding by placing a fluid-filled isovolumic balloon in the left ventricular ...

Adverse left ventricular (LV) remodeling after acute myocardial infarction is characterized by LV dilatation and development of a fibrotic scar, and is a critical factor for the prognosis of subsequent development of heart failure. Although myofiber organization is recognized as being important for preserving physiological cardiac function and structure, the anatomical features of injured myofi...

On the hypothesis that coronary sinus occlusion (CSO) may reduce myocardial ischemia, we examined the effects of CSO on coronary collateral blood flow and on the distribution of regional myocardial blood flow (RMBF) in dogs. Thirty-eight anesthetized dogs underwent occlusion of the left anterior descending coronary artery with or without CSO and intact vasomotor tone. We measured RMBF and intra...

This study compared the transmural distribution of high-energy phosphate (HEP) depletion during oxidative stress induced by pacing- and dobutamine-induced tachycardia in myocardium perfused by a flow-limiting coronary stenosis. Myocardial blood flow (MBF) was measured with radioactive microspheres. Creatine phosphate (CrP), ATP, and Pi were measured with transmurally localized 31P NMR spectrosc...